The 75-year-old has been in office since 2009, and is set to end that term in 2019. The ANC leadership however met on Monday and decided that he had to leave the presidency.
“It was very unfair to me that this issue is raised,” Zuma said during an interview with state broadcaster SABC.
“Nobody has ever provided the reasons. Nobody is saying what I have done,” he added.
The president said the ANC had not followed proper procedures in trying to unseat him.
Earlier, ruling African National Congress party said the parliament could elect a new president as early as Thursday if Zuma steps down.
The ANC’s secretary-general Ace Magashule on Tuesday said the ANC would back an impeachment motion in parliament.
The two fell out in 2016, with Ramaphosa disagreeing with Zuma’s decisions in public.